1. Field of the Invention
The present invention relates to a vehicle headlamp used as a lamp for a vehicle and, in particular, relates to a vehicle headlamp which employs a semiconductor light emitting element as a light source.
2. Description of the Related Art
As a lamp for a vehicle such as a headlamp, for example, there are a projector-type and a paraboloidal reflector-type. The projector-type vehicle lamp is configured in a manner that a light emitted from a light source disposed on an optical axis is reflected toward the forward direction by a reflector and is converged close to the optical axis. The reflected light is irradiated in the forward direction of the lamp via a projection lens disposed on the forward side of the reflector. On the other hand, the paraboloidal reflector-type vehicle lamp is configured to include a light source disposed on an optical axis and a reflector, which is formed so as to have, as a reference surface, a rotating paraboloidal surface having a focal point near the light source. A light emitted from the light source is reflected toward the forward direction by the reflector as a parallel light so that the reflected light is irradiated in the forward direction of the lamp.
The projector-type vehicle lamp is smaller in the diameter of the reflector as compared with that of the paraboloidal reflector-type vehicle lamp. Therefore, the projector-type vehicle lamp can be miniaturized in its size. However, in the case where the discharge light emitting portion of a discharge bulb or the filament of a halogen lamp is used as the light source, in order to control the reflection of light from the light source suitably or to secure a space for attaching the light source, the reflector is required to have a certain size even for the projector-type vehicle lamp. Further, since a heat value of the light source is large, the size of the reflector is required to be set in view of the influence of the heat. Thus, it is difficult to further miniaturize the lamp.
In view of above, there is proposed a lamp which employs an LED (light emitting diode), for example, as a semiconductor light emitting element for a light source (for example, see Japanese Patent Unexamined Publication JP-A-2004-95480, pages 3 to 9, FIGS. 1, 3, 6 and 10).
When the light source is configured by an LED, since the light source can be treated as an almost point light source, the diameter of the reflector can be made small. Further, since it is not required for the reflector to secure a large attachment space nor to take the influence of the heat from the LED into consideration, the lamp can be made smaller as compared with the case where the discharge light emitting portion of the discharge bulb or the filament of the halogen lamp is used as the light source.
The related art is arranged to selectively use two kinds of lamp units among a plurality of lamp units, that is, a projector-type lamp unit, a direct-projection-type lamp unit and a reflection-type lamp unit, so that light distribution patterns with different light distribution characteristics can be formed easily.
However, in the related art, since the respective lamp units are configured separately, the entire volume of the lamp becomes large and so the miniaturization of the lamp can not be realized sufficiently.